Monthly Archives: May 2016

Here is a list of species described from May 22 to May 31. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa and International Journal of Systematic and Evolutionary Microbiology.

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The rainforests of Central and South America host this small but scary creature, the bullet ant Paraponera clavata. Feared by people living where it is found, the bullet ant is one of the most venomous ants in the world. The name “bullet ant” is a reference to the pain caused by being shot, which is said to be the closest analogy to the pain of a bullet ant sting. In Portuguese it is known as tocandira, a word derived from Tupi, meaning “hurting very much”. In Spanish it is sometimes called “hormiga 24 horas” because the pain is said to last a whole day.

A bullet ant worker. Photo by Geoff Gallice.*

The bullet ant is found in the Neotropical Ecozone from Honduras and Nicaragua to Paraguay. Their nests are built at the base of the trees, under the ground, and workers look for food mostly on the tree trunk and canopy directly above the nest and on nearby trees, sometimes exploring the forest floor. They are predatory ants, feeding mainly on arthropods, but also consuming nectar.

Considered a primitive ant, the bullet ant lacks polymorphism among the worker caste, i.e., all workers have the same general appearance. The queen is also not very different from the workers.

The horrible sting inflicted by these ants is used as a form of defence. It contains a neurotoxin known as poneratoxin that causes paralysis by blocking synaptic transmission. It is effective against at least vertebrates and arthropods. Nevertheless, the Sateré-Mawé people from Brazil use the ants’ stings in a sadic ritual to become a “warrior”. For this purpose, a poor boy has to put his hand inside a glove filled with bullet ants and let it there for 10 minutes. As a result the boy’s arm becomes paralyzed for days and he may shake incontrollably due to the venom’s effect. And he has to repeat this ritual 20 times!

Males and females are defined by their gametes. Males have tiny, usually mobile gametes, while females have very large gametes that usually do not move. This means that females produce less gametes, but put a lot of resources in each one, i.e., female gametes are expensive. On the other hand, male gametes are very cheap, small and produced in large quantities. As a result of these differences, males and females have different interests during sex.

As females produce more expensive and less numerous gametes, they tend to be very selective on who they let fertilize them. But males benefit from fertilizing every female gamete they find in their way. In other words, females want quality and males want quantity. This difference in interests is called sexual conflict and is a strong evolutionary force.

One evolutionary adaptation that has been seen as resulting from sexual conflict is the mating system in odonates (dragonflies and damselfies). During sex, the male dragonfly grasps the female neck using a grapsing apparatus at the end of its abdomen. The female is then induced to connect the tip of its abdomen to the second and third segments of the male’s abdomen, where sperm is stored. The couple than flies together in a heart-like formation.

Two dragonflies of the species Rhionaeschna multicolor copulating. The male is the blue one, which is grasping the female’s neck and making her touch the tip of her abdomen to his second and third abdominal segments, where sperm is stored. Photo by Eugene Zelenko.

It was thought that the male grasping apparatus forced an unwilling female to copulate with him, suggesting that the organ evolved through sexual conflict. The fact that males usually grab females way before they accept to mate and continue to hold them for a long time after the mating has finished (preventing her from mating with other males) seem to be good evidence for this theory. If this is true, than the female would try to get rid of the male, selecting stronger and bigger grasping apparatuses in males, as those would be more efficient in holding the female and, as a result, would lead to more descendants.

A study published last year tested this hypothesis. Córdoba-Aguilar et al. (2015) evaluated the allometry (the proportional size of a structure with respect to body size) of the male grasping apparatus in several dragonfly species. If males forced females to copulate, a hyperallometric relationship should be expected.

What does that mean? Well, let’s try to explain it the simplest way. When you plot data on the size of a structure according to the size of the body as a whole on a graph, using values that lead to a linear relationship, you may have different results. The structure may increase in size in the same way as the body, in a 1:1 relationship. In this case, the line in the graph is said to have a slope equal to 1 and there is an isometric relationship of the structure to the body. If the slope is greater than one, this means that the structure grows faster than the body, having a hyperallometric relationship. If the slope is smaller than one (but greater than zero), the relationship is hypoallometric and the structure grows slower than the body.

The measurements of the grasping apparatus in dragonflies in general showed an isometric relationship. So, according to this approach, the structure did not evolve as a “weapon” to subdue females. But which other explanations may exist then? It could be used as a courtship tool, a way for the male to convince the female to mate with him. It could also be a way to avoid interspecific mating, as the grasping apparatus has a strong specificity in shape to the female neck of the same species. A male dragonfly cannnot grasp a female of other species because the grasping apparatus simply does not fit in the female’s neck.

Both alternative hypotheses for the evolution of the apparatus are possible, but further studies are needed to test them.

Here is a list of species described from May 15 to May 21. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa and International Journal of Systematic and Evolutionary Microbiology.

Chilicola charizard is a bee described this week whose name is a reference to one of the most famous Pokémon.

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Today we are going back to Madagascar, that weird African island that fights against Australia for the title of the most bizarre place on Earth. We already presented one of its inhabitants, the Grandidider’s Baobab, and today I’ll show you a tiny and unusual beetle, the giraffe weevil, Trachelophorus giraffa.

A male giraffe weevil. Photo by Frank Vassen*

The reason of the name of this adorable creature is obvious at first sight. The unusual long neck most likely evolved through sexual selection, as it is three times longer in males than in females. Despite looking as something very inconvenient, the giraffe weevil’s neck is actually useful in helping it to roll leaves in order to build a nest.

Measuring only about 2.5 cm in length, it is a considerably popular animal in lists of weird creatures, but unfortunately little is known about its life history and, just as virtually all life forms in the island, is threatened by habitat loss.

Here is a list of species described from May 8 to May 14. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa and International Journal of Systematic and Evolutionary Microbiology.

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Running delicately on the tip of its feet like a ballerina, our first crustacean fellow comes from the Pacific coast of the Americas and is commonly called “sally lightfoot”. Scientifically it is known as Grapsus grapsus, a name that sounds like something gnawing, or grasping, as if it was intended to represent its large claws and small mouth working together to scratch algae from the rocky shores it inhabits.

A sally lightfoot in the Galapagos Islands. Photo by A. Davey.* (flickr.com/photos/adavey/)

The sally lightfoot is found on the Pacific coasts of the Americas from Mexico to northern Chile, in the Galapagos Islands and in several Islands in the western Atlantic, such as the Caribbean Islands and the Saint Peter and Saint Paul Archipelago in Brazil. Specimens from the Pacific usually grow up to 80 mm or more in length, while those in the Saint Paul Island are smaller, reaching about 70 mm. Males are slightly larger than females.

As most crabs, the sally lightfoot is a detritivore, feeding on dead animals and other detrites, but seems to be primarily a herbivore, feeding on algae that it scrapes (graps graps graps…) off rocks. It can also, eventually, capture small animals, and there are reports of specimens having a relationship as cleaners with marine iguanas in the Galapagos Islands, scraping ticks (graps graps graps…) of the iguanas’ skin.